Chemosensory mechanisms in the vertebrate taste bud have eluded detailed analyses until recently, mainly due to the relative inaccessibility of the taste cells. A particularly important question is how signals are processed in the peripheral taste organs. Ultrastructural studies have shown that there are synapses between taste cells and gustatory axons as well as between taste cells, themselves, raising the possibility that there is synaptic processing in the taste bud. We have recently employed a new approach that will allow us to examine the microphysiology of taste cells in a relatively intact, but exposed preparation and to begin to answer these questions. This preparation consists of a thin slice of lingual epithelium, mounted in a shallow. transparent chamber in such a way that entire taste buds and their cells can be visualized in the living isolated tissue. The objective of the following proposal is to test the hypothesis that there are synaptic connections among cells in the taste bud and that the final output, activity in gustatory sensory axons, represents a complex integration of signals from several different cells within the taste bud. Thus, we propose the following specific aims for the project: 1) We propose to confirm and extend our preliminary findings suggesting that there are synaptic connections between receptor and basal cells: 2) We will examine the properties of these synaptic connections, namely their Ca-dependence, neurotransmitter type, ionic mechanisms and response to repetitive and/or prolonged activation: 3) We will determine whether synaptic connections between receptor cells and basal cells are bidirectional and/or reciprocal, as their morphology suggests. The results of these studies will provide information relevant to signal processing in chemosensory receptor organs in general, such as carotid body responses. Furthermore, the data may provide a baseline for studying the question of how taste stimuli are coded in the vertebrate taste bud.